This application requests continuation of the Iowa Cochlear Implant Clinical Research Center. We are engaged in clinical outcomes research studying the application of cochlear implants (Cl) in children and adults. CIs have been successful in providing speech perception to postlingually deafened adults and prelingually deafened children in quiet. Larger populations of hearing impaired subjects, such as those with high-frequency loss and preserved low frequency might also benefit from electrical speech processing. This application plans to refine the criteria for acoustic + electric hearing, study speech in noise, examine the advantages of binaural implantation in adults and children, examine outcomes when age of implantation is reduced to 7 months, and improve the perception of music with implants. All are important issues confronting researchers and clinicians. The overall goals of the proposed research are 1) To determine the boundaries of selection criteria for the acoustic and electrical speech processing implants, 2) Improve and study the benefits of binaural cochlear implants in adults and children using more realistic soundfield hearing tests, 3) Determine if a less invasive electrode in one ear and standard Cl in the other provides similar outcomes as bilateral standard CIs, 4) Refine and expand the way in which electrophysiological measures of auditory function can be used to understand how the auditory system responds to electrical stimulation, 5) Investigate those factors that influence music perception and enjoyment of Cl recipients, and 6) Describe and explain individual differences in perceptual, linguistic, and social outcomes of individuals receiving cochlear implants in childhood. The proposed application will study 372 previously implanted adults and children, 105 newly recruited postlingually deafened adults, and 70 prelingually and postlingually deafened children. Postlingually deafened adults and children with residual low frequency hearing and reduced speech perception will receive implants designed to preserve residual hearing. Binaural implants will be studied in both adults and children. Five research subprojects, an administrative Core A, and Patient Care, Speech Processing, and Technical Core B will address the above goals. The five research subprojects are highly integrated and depend on data from each other to answer the experimental questions proposed.